List of all special characters that need to be esc

问题:

I am trying to create an application that matches a message template with a message that a user is trying to send. I am using Java regex for matching the message. The template/message may contain special characters.

How would I get the complete list of special characters that need to be escaped in order for my regex to work and match in the maximum possible cases?

Is there a universal solution for escaping all special characters in Java regex?

回答1:

You can look at the javadoc of the Pattern class: http://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html

You need to escape any char listed there if you want the regular char and not the special meaning.

As a maybe simpler solution, you can put the template between \Q and \E - everything between them is considered as escaped.

回答2:

• Java characters that have to be escaped in regular expressions are:
  \.[]{}()<>*+-=?^$|
• Two of the closing brackets (] and }) are only need to be escaped after opening the same type of bracket.
• In []-brackets some characters (like + and -) do sometimes work without escape.

回答3:

To escape you could just use this from Java 1.5:

Pattern.quote("$test");

You will match exacty the word $test

回答4:

According to the String Literals / Metacharacters documentation page, they are:

<([{\^-=$!|]})?*+.>

Also it would be cool to have that list refereed somewhere in code, but I don't know where that could be...

回答5:

On @Sorin's suggestion of the Java Pattern docs, it looks like chars to escape are at least:

\.[{(*+?^$|

回答6:

Combining what everyone said, I propose the following, to keep the list of characters special to RegExp clearly listed in their own String, and to avoid having to try to visually parse thousands of "\\"'s. This seems to work pretty well for me:

final String regExSpecialChars = "<([{\\^-=$!|]})?*+.>";
final String regExSpecialCharsRE = regExSpecialChars.replaceAll( ".", "\\\\$0");
final Pattern reCharsREP = Pattern.compile( "[" + regExSpecialCharsRE + "]");

String quoteRegExSpecialChars( String s)
{
    Matcher m = reCharsREP.matcher( s);
    return m.replaceAll( "\\\\$0");
}

回答7:

on the other side of the coin, you should use "non-char" regex that looks like this if special characters = allChars - number - ABC - space in your app context.

String regepx = "[^\\s\\w]*";

回答8:

Not sure I fully understand your question, but I think you should look at Matcher.quoteReplacement()